Conical intersections (CIs) provide effective fast nonradiative decay pathways for electronic excitation, which can significantly influence molecular photoluminescence properties. However, in many cases, crossing a CI does not have direct observables, making studies of CIs experimentally challenging. Herein, the theoretically predicted double CIs by cis–trans twisting and cyclization in tetraphenyl ethylene, a well-known aggregation-induced emission molecule, are investigated with excitation dependent ultrafast UV/IR spectroscopy and fluorescence. Both the fluorescence quantum yield and the efficiency of cyclization are found to be smaller with a shorter excitation wavelength. An abrupt change occurs at about 300–310 nm. The results imply that crossing the twisting CI has a larger barrier than the cyclization CI, and the cis–trans twisting motion is probably involved with large solvation reorganization.
Double crossing conical intersections and anti-Vavilov fluorescence in tetraphenyl ethylene
Zhuowei Hou, Jianxin Guan, Jie Peng, Xinmao Li, Zhihao Yu, Junrong Zheng; Double crossing conical intersections and anti-Vavilov fluorescence in tetraphenyl ethylene. J. Chem. Phys. 14 April 2022; 156 (14): 144302. https://doi.org/10.1063/5.0082679
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